Data commit

Task/Sierpinski-triangle/Haskell/sierpinski-triangle-1.hs

@@ -0,0 +1,7 @@
+sierpinski 0 = ["*"]
+sierpinski n = map ((space ++) . (++ space)) down ++
+               map (unwords . replicate 2) down
+    where down = sierpinski (n - 1)
+          space = replicate (2 ^ (n - 1)) ' '
+
+main = mapM_ putStrLn $ sierpinski 4

Task/Sierpinski-triangle/Haskell/sierpinski-triangle-2.hs

@@ -0,0 +1,14 @@
+import Data.List (intercalate)
+
+sierpinski :: Int -> [String]
+sierpinski 0 = ["▲"]
+sierpinski n =
+  [ flip
+      intercalate
+      ([replicate (2 ^ (n - 1))] <*> " -"),
+    (<>) <*> ('+' :)
+  ]
+    >>= (<$> sierpinski (n - 1))
+
+main :: IO ()
+main = mapM_ putStrLn $ sierpinski 4

Task/Sierpinski-triangle/Haskell/sierpinski-triangle-3.hs

@@ -0,0 +1,9 @@
+import Data.Bits ((.&.))
+
+sierpinski n = map row [m, m-1 .. 0] where
+	m = 2^n - 1
+	row y = replicate y ' ' ++ concatMap cell [0..m - y] where
+		cell x	| y .&. x == 0 = " *"
+			| otherwise = "  "
+
+main = mapM_ putStrLn $ sierpinski 4

Task/Sierpinski-triangle/Haskell/sierpinski-triangle-4.hs

@@ -0,0 +1,25 @@
+import Data.List (intersperse)
+
+-- Top down, each row after the first is an XOR / Rule90 rewrite.
+-- Bottom up, each line above the base is indented 1 more space.
+sierpinski :: Int -> String
+sierpinski = fst . foldr spacing ([], []) . rule90 . (2 ^)
+  where
+    rule90 = scanl next "*" . enumFromTo 1 . subtract 1
+      where
+        next =
+          const
+            . ( (zipWith xor . (' ' :))
+                  <*> (<> " ")
+              )
+        xor l r
+          | l == r = ' '
+          | otherwise = '*'
+    spacing x (s, w) =
+      ( concat
+          [w, intersperse ' ' x, "\n", s],
+        w <> " "
+      )
+
+main :: IO ()
+main = putStr $ sierpinski 4

Task/Sierpinski-triangle/Haskell/sierpinski-triangle-5.hs

@@ -0,0 +1,17 @@
+sierpinski :: Int -> [String]
+sierpinski n =
+  foldr
+    ( \i xs ->
+        let s = replicate (2 ^ i) ' '
+         in fmap ((s <>) . (<> s)) xs
+              <> fmap
+                ( (<>)
+                    <*> (' ' :)
+                )
+                xs
+    )
+    ["*"]
+    [n - 1, n - 2 .. 0]
+
+main :: IO ()
+main = (putStrLn . unlines . sierpinski) 4